Automatic transmission system with time-delay circuit

ABSTRACT

An automatic transmission system wherein the amount of slip in a torque converter constituting a part of the transmission is utilized as a major factor for determining a shift point, and logic circuitry is incorporated to provide a means for this purpose and to issue a shift instruction which best suits the gear changing conditions, so that an actuator is brought into action by means of a hydraulic actuation circuit to accomplish the gear change, and a time-delay circuit is also incorporated in the said logic circuitry.

United States Patent Wakamatsu et al. [451 Aug. 15, 1972 [54] AUTOMATIC TRANSMISSION SYSTEM [56] References Cited WITH TIME-DELAY CIRCUIT UNITED STATES PATENTS [72] Inventors: Hisato Wakamatsu, Karrya; Takaolo 2,498,600 2/1950 Brunken.. ..v....74/731 x Kato, Toyohashr; Mamoru Kawaku- 2,529,129 11/1950 Blair ..74/731 |30; Kaslwn' 0, both 0f Kaliya, all 2,952,346 9/ 1960 Costa et al. ..74/365 X of Japan Y 3,147,595 9/1964 Liang ..74/731 x 3 267 762 8/1966 Reval ..74/866 X [73] Assignee. Nlppondenso Kabushlkl Kalsha,

Karyahi Japan 3,448,640 6/ 1969 I Nelson ..74/866 [22] Filed: i Y June 23, 1970 Primary Examiner-Carlton R. Croyle or [30] Foreign Application Priority Data [57] ABSTRACT June 26, 1969 Japan .A4/50882 An automatic transmission system wherein the amount of slip in .a torque convener constituting a part of the [52] U.s.` c1. ..74/731 transmission is utilized as a maior factor for dcrcrmiri [51] int c1. F1611 47/08, 360k 23/00 ing a shift point, and logic circuitry iS incorporated to [581 Field 6r Search ..74/731, 645, 866 providc a means for this Purpose arid to issue a Shifi instruction which best suits the gear changing conditions, so that an actuator is brought into action'by means of a hydraulic actuation circuit to accomplish the gear change, and a time-delay circuit is also incorporated in the said logic circuitry.

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PTENTHUB 1 5 1972 SHEET OlUF 18 INVENTORS BY Z 5 PATENYEDAUS 15 |912 SHEET US UF 18 INVENTOR 3 EY j 7 ATTORNEYS PATENTEDAus 15 912 SHEET O'UF 18 SHEET UBUF 18 PATENTEDAus 15 |912 PATENTEDAus 1s |972 SHEET lUF 18 PATENTED 1111; 1 s 11112 SHEET 1lUF18 PATENTEDMIG 15 |9124 SHEET 12 or 1a f1 L ATTORNEYB BY /Y SHEET 1M UF 18 PATENIEDMIB 15 |912 L, A'VVORNIEYB SHEET 15 QF 18 PATENTEDAUG 15 |912 TTORNEYS SHEET IBF 18 PATENTEDAuc 1s |972 BY /m Cr ATTORNEY s PATENTEDAUG 15 |912 SHEET 18UF 18 ATTORNEY QJ BACKGROUND OF THE INVENTION 1. FIELD OF THE INVENTION The present invention relates to transmissions for automobiles and the like and more particularly to an automatic transmission system comprising a fluid torque converter and a multi-range transmission gear.

2. DESCRIPTION OF THE PRIOR ART In the conventional automatic transmissions used with ordinary passenger cars, the shift points are determined according to a signal representing the vehicle speed (which signal being derived from the Output shaft of a multi-range transmission gear)l or a signal representing the number of revolutions of an internal combustion engine which is a prime mover and the inlet manifold vacuum (boost pressure) of the internal combustion engine or the degree of depression of an accelerator pedal operated by the driver. These signals are provided in the form of oil pressures of varying values, and the shift points are determined and the valves are opened or closed according to the correlation between these two varying oil pressures so as to selectively operate by the oil pressures an actuator for multi-plate clutches, brake bands and the like. In other words, all the controls are effected by means of oil pressures, which means that the detected signals in the form of oil pressures generally tend to be subjected to errors and thus accurate controls cannot be expected. Consequently, the shift points also tend to be subjected to errors. Furthermore, since the hydraulic actuation circuit is generally complicated in construction, it is not an easy matter to provide the circuit with an improved function over what is presently available. For` example, there is an inconvenience in that when a rapid speed reduction is required while driving up a hill at a relatively high speed, the releasingthe pressure on the ac celerator pedal first causes a shift to a high gear and then the vehicle slows down, so that if the accelerator pedal is redepressed to accelerate right after the speed reduction, it results in a shift to a lower gear ratio. Moreover, in spite of the fact that engine braking is required when the vehicle is descending a hill at a relatively high speed, the vehicle speed tends to increase thus preventing an automatic shift to the most appropriate low gear ratio, and in order to avoid this in such a case it is necessary to manually effect a shift to low gear.

On the other hand, when driving on a mountain road with many upgrades and downgrades, for example, in order to provide engine braking through an ordinary three-speed automatic transmission, the second gear is employed for descending hills. However, if the accelerator pedal is depressed to increase the output of an internal combustion engine in order to ascend an upgrade immediately after the vehicle has descended a downgrade, it gives rise to an inconvenience that the gear ratio is automatically upshifted to the top gear so that there is a shortage in the accelerating force required for climbing hills. In order to eliminate this inconvenience, that is, in order to ensure the required accelerating force for climbing, the gear ratio is downshifted again to the second gear.

These are the essential drawbacks attributable to the fact that the shift points are determined according to only the load condition of the internal combustion engine and the vehicle speed and that no internal conditions ofthe transmission are taken into consideration as controlling factors.

SUMMARY OF THE INVENTION The present invention is characterized in that the amount of slip in a torque converter constituting an essential element of a transmission is utilized as a major factor for determining the shift points, and, as a means for this purpose, a logic circuit consisting of electronic circuitry is incorporated to provide a proper shifting instruction that best suits the shifting conditions, so that an actuator is operated through a hydraulic actuation circuit to accomplish the gear change, and at the same time a time-delay circuit is also incorporated in the logic circuit.

Accordingly, the present invention has for its object the provision of a transmission which incorporates various improvements in that a proper shifting function is ensured not only during normal driving, but also when the engine is used as a brake on decents, that the mechanical structure of the hydraulic system relating to the operation of the actuator and the like is simplified and that consequently shift points are prevented from being thrown off due to Oil pressure changes.

Another object ofthe present invention is the provision of a transmission which is so designed that when the gear changing conditions are met to change from low to high gear as will be the case when the vehicle has just descended a hill and immediately thereafter there are provided other gear changing conditions to change the gear ratio into the low gear, the above-mentioned time-delay circuit is brought into operation so that despite the establishment of the first-mentioned shifting conditions a shift which would otherwise take place is delayed for a certain time to thereby eliminate those inconveniences that will be caused if such a shift were allowed to occur. This transmission has thus a more reliable and more sophisticated function.

The most important feature of the present invention resides in the arrangement of an automatic transmission with its principal part being divided broadly into a torque converter transmission, a hydraulic actuation circuit and an electronic logic circuit.

A further object of the present invention is to provide an automatic transmission system having a timedelay circuit compiising a transmission equipped with a torque converter including a torque converter pump coupled with the input shaft and a torque converter turbine coupled with the input shaft of a transmission gear, friction engaging means for attaining gear changingengagements of said transmission gear in said transmission, a hydraulic actuation circuit for controlling said friction engaging means including a gear change region establishing valve and a distributor valve for distributing working oil to said friction engaging means, a first detecting means for producing an electrical signal proportional to the rotational speed of the torque converter input shaft, a second detecting means for producing an electrical signal proportional to the rotational speed of either the input shaft or the output shaft of the transmission gear, an operational circuit adapted to receive as input signals the output electrical signals from said first and second detecting means so as to 

1. An automatic transmission system with a time-delay circuit comprising: a transmission having an input shaft and transmission gearing connected to a gearing shaft and being provided with a torque converter including a torque converter pump coupled to the said input shaft and a torque converter turbine coupled to the gearing shaft; friction engaging means for effecting gear changing engagements of said transmission gearing in said transmission; a hydraulic actuation circuit for controlling said friction engaging means including a shift region setting valve and a distributor valve for distributing working oil to said friction engaging means; first detecting means for producing an electrical signal proportional to the rotational speed of said torque converter input shaft; second detecting means for producing the an electrical signal proportional to the rotational speed of the gearing shaft of said transmission gearing; slip ratio operating circuit means connected to receive as inputs signals thereto the output electrical signals from said first and second detecting means so as to compute the ratio of the rotational speed of said torque converter input shaft to the rotational speed of the shaft of said transmission gearing for providing output signals only when said ratio exceeds at least one predetermined value and only when said ratio is less than at least one other predetermined value; time-delay circuit means for delaying a given one of the output signals from said operating circuit means for a predetermined time such that said given output signal is passed through said time-delay circuit means only when said given output signal has lasted longer than said predetermined time; and means including logic circuit means connected to said slip ratio operating circuit means and said time-delay circuit means for actuating said distributor valve of said hydraulic actuation circuit to change the gear changing engagements of the transmission gearing forthwith except when prevented at all because said given output signal from said time-delay circuit exists for less than said predetermined time or when that given output signal exists for more than said predetermined time and prevents said change in the gear changing engagements only during that predetermined time.
 2. An automatic transmission system with a time-delay circuit comprising: a transmission having an input shaft and transmission gears having input and output shafts, said transmission being provided with a torque converter including a torque converter turbine coupled to the input shaft of said transmission gears; friction engaging means for effecting gear changing engagements of said transmission gears in said transMission; a hydraulic actuation circuit for controlling said friction engaging means including a shift region setting valve and a distributor valve for distributing working oil to said friction engaging means; first means for producing an electrical signal proportional to the rotational spaced of the input shaft of said torque converter; second means for producing an electrical signal proportional to the rotational speed of said input shaft of said transmission gears; third means for producing an electrical signal proportional to the rotational speed of said output shaft of said transmission gears; an arithmetic circuit for receiving as input signals thereto the output electrical signals from said first and second means to perform an arithmetic operation on said input signals to produce a signal indicating one of predetermined regions which corresponds to the speed ratio of the rotational speed of said torque converter input shaft to that of said transmission gear input shaft, said arithmetic circuit further receiving as its input signal the output signal from said third means and comparing it with a reference signal to produce a signal indicating the magnitude of the rotational speed of said transmission gear output shaft; a logic circuit for receiving the signal from said arithmetic circuit to perform a logical operation thereon to produce a signal for actuating said distributor valve in said hydraulic actuation circuit; and a time-delay circuit for delaying the output speed ratio signal from said arithmetic circuit corresponding to one of said predetermined regions by a predetermined time so as to pass therethrough said output speed ratio signal from said arithmetic circuit only when said output speed ratio signal lasts longer than said delay time. 